package com.github.link2fun.support.utils.sign;

/**
 * Base64工具类
 *
 * @author ruoyi
 */
@SuppressWarnings("unused")
public final class Base64 {
  static private final int BASELENGTH = 128;
  static private final int LOOKUPLENGTH = 64;
  static private final int TWENTYFOURBITGROUP = 24;
  static private final int EIGHTBIT = 8;
  static private final int SIXTEENBIT = 16;
  static private final int FOURBYTE = 4;
  static private final int SIGN = -128;
  static private final char PAD = '=';
  static final private byte[] base64Alphabet = new byte[BASELENGTH];
  static final private char[] lookUpBase64Alphabet = new char[LOOKUPLENGTH];

  static {
    for (int i = 0; i < BASELENGTH; ++i) {
      base64Alphabet[i] = -1;
    }
    for (int i = 'Z'; i >= 'A'; i--) {
      base64Alphabet[i] = (byte) (i - 'A');
    }
    for (int i = 'z'; i >= 'a'; i--) {
      base64Alphabet[i] = (byte) (i - 'a' + 26);
    }

    for (int i = '9'; i >= '0'; i--) {
      base64Alphabet[i] = (byte) (i - '0' + 52);
    }

    base64Alphabet['+'] = 62;
    base64Alphabet['/'] = 63;

    for (int i = 0; i <= 25; i++) {
      lookUpBase64Alphabet[i] = (char) ('A' + i);
    }

    for (int i = 26, j = 0; i <= 51; i++, j++) {
      lookUpBase64Alphabet[i] = (char) ('a' + j);
    }

    for (int i = 52, j = 0; i <= 61; i++, j++) {
      lookUpBase64Alphabet[i] = (char) ('0' + j);
    }
    lookUpBase64Alphabet[62] = (char) '+';
    lookUpBase64Alphabet[63] = (char) '/';
  }

  private static boolean isWhiteSpace(char octect) {
    return (octect == 0x20 || octect == 0xd || octect == 0xa || octect == 0x9);
  }

  private static boolean isPad(char octect) {
    return (octect == PAD);
  }

  private static boolean isData(char octect) {
    return (octect < BASELENGTH && base64Alphabet[octect] != -1);
  }

  /**
   * Encodes hex octects into Base64
   *
   * @param binaryData Array containing binaryData
   * @return Encoded Base64 array
   */
  public static String encode(byte[] binaryData) {
    if (binaryData == null) {
      return null;
    }

    int lengthDataBits = binaryData.length * EIGHTBIT;
    if (lengthDataBits == 0) {
      return "";
    }

    int fewerThan24bits = lengthDataBits % TWENTYFOURBITGROUP;
    int numberTriplets = lengthDataBits / TWENTYFOURBITGROUP;
    int numberQuartet = fewerThan24bits != 0 ? numberTriplets + 1 : numberTriplets;
    char encodedData[] = null;

    encodedData = new char[numberQuartet * 4];

    byte k = 0, l = 0, b1 = 0, b2 = 0, b3 = 0;

    int encodedIndex = 0;
    int dataIndex = 0;

    for (int i = 0; i < numberTriplets; i++) {
      b1 = binaryData[dataIndex++];
      b2 = binaryData[dataIndex++];
      b3 = binaryData[dataIndex++];

      l = (byte) (b2 & 0x0f);
      k = (byte) (b1 & 0x03);

      byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
      byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);
      byte val3 = ((b3 & SIGN) == 0) ? (byte) (b3 >> 6) : (byte) ((b3) >> 6 ^ 0xfc);

      encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
      encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];
      encodedData[encodedIndex++] = lookUpBase64Alphabet[(l << 2) | val3];
      encodedData[encodedIndex++] = lookUpBase64Alphabet[b3 & 0x3f];
    }

    // form integral number of 6-bit groups
    if (fewerThan24bits == EIGHTBIT) {
      b1 = binaryData[dataIndex];
      k = (byte) (b1 & 0x03);
      byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
      encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
      encodedData[encodedIndex++] = lookUpBase64Alphabet[k << 4];
      encodedData[encodedIndex++] = PAD;
      encodedData[encodedIndex++] = PAD;
    } else if (fewerThan24bits == SIXTEENBIT) {
      b1 = binaryData[dataIndex];
      b2 = binaryData[dataIndex + 1];
      l = (byte) (b2 & 0x0f);
      k = (byte) (b1 & 0x03);

      byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
      byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);

      encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
      encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];
      encodedData[encodedIndex++] = lookUpBase64Alphabet[l << 2];
      encodedData[encodedIndex++] = PAD;
    }
    return new String(encodedData);
  }

  /**
   * Decodes Base64 data into octects
   *
   * @param encoded string containing Base64 data
   * @return Array containind decoded data.
   */
  public static byte[] decode(String encoded) {
    if (encoded == null) {
      return null;
    }

    char[] base64Data = encoded.toCharArray();
    // remove white spaces
    int len = removeWhiteSpace(base64Data);

    if (len % FOURBYTE != 0) {
      return null;// should be divisible by four
    }

    int numberQuadruple = (len / FOURBYTE);

    if (numberQuadruple == 0) {
      return new byte[0];
    }

    byte decodedData[] = null;
    byte b1 = 0, b2 = 0, b3 = 0, b4 = 0;
    char d1 = 0, d2 = 0, d3 = 0, d4 = 0;

    int i = 0;
    int encodedIndex = 0;
    int dataIndex = 0;
    decodedData = new byte[(numberQuadruple) * 3];

    for (; i < numberQuadruple - 1; i++) {

      if (!isData((d1 = base64Data[dataIndex++])) || !isData((d2 = base64Data[dataIndex++]))
        || !isData((d3 = base64Data[dataIndex++])) || !isData((d4 = base64Data[dataIndex++]))) {
        return null;
      } // if found "no data" just return null

      b1 = base64Alphabet[d1];
      b2 = base64Alphabet[d2];
      b3 = base64Alphabet[d3];
      b4 = base64Alphabet[d4];

      decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
      decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
      decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);
    }

    if (!isData((d1 = base64Data[dataIndex++])) || !isData((d2 = base64Data[dataIndex++]))) {
      return null;// if found "no data" just return null
    }

    b1 = base64Alphabet[d1];
    b2 = base64Alphabet[d2];

    d3 = base64Data[dataIndex++];
    d4 = base64Data[dataIndex++];
    if (!isData((d3)) || !isData((d4))) {// Check if they are PAD characters
      if (isPad(d3) && isPad(d4)) {
        if ((b2 & 0xf) != 0)// last 4 bits should be zero
        {
          return null;
        }
        byte[] tmp = new byte[i * 3 + 1];
        System.arraycopy(decodedData, 0, tmp, 0, i * 3);
        tmp[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
        return tmp;
      } else if (!isPad(d3) && isPad(d4)) {
        b3 = base64Alphabet[d3];
        if ((b3 & 0x3) != 0)// last 2 bits should be zero
        {
          return null;
        }
        byte[] tmp = new byte[i * 3 + 2];
        System.arraycopy(decodedData, 0, tmp, 0, i * 3);
        tmp[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
        tmp[encodedIndex] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
        return tmp;
      } else {
        return null;
      }
    } else { // No PAD e.g 3cQl
      b3 = base64Alphabet[d3];
      b4 = base64Alphabet[d4];
      decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
      decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
      decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);

    }
    return decodedData;
  }

  /**
   * remove WhiteSpace from MIME containing encoded Base64 data.
   *
   * @param data the byte array of base64 data (with WS)
   * @return the new length
   */
  private static int removeWhiteSpace(char[] data) {
    if (data == null) {
      return 0;
    }

    // count characters that's not whitespace
    int newSize = 0;
    int len = data.length;
    for (int i = 0; i < len; i++) {
      if (!isWhiteSpace(data[i])) {
        data[newSize++] = data[i];
      }
    }
    return newSize;
  }
}
